Impulse starting and operating circuit for gas discharge lamps



Nov. 4, 1969 A. R. HALLAY 3,476,977

IMPULSE STARTING AND OPERATING CIRCUIT FOR GAS DISCHARGE LAMPS Filed May 31, 1967 2 Sheets-Sheet 1 INVENTOR- AIeflnderE/fiI/ay,

Nov. 4, 1969 A. R. HALLAY 3,475,977-

IMPULSE STARTING AND OPERATING CIRCUIT FOR GAS DISCHARGE LAMPS Filed May 31. 19s? 2 Sheets-Sheet ll r/fl' w 70 L! p 44 a //4 6'8 79 Q Fig.5

INVENTOR. A/gandarFf/al/qg United s ate Pa e t?) IMPULSE STARTING AND OPERATING CIRCUIT FOR GAS DISCHARGE LAMPS Alexander R. Hallay, Fort Wayne, Ind., assignor to General Electric Company, a corporation of New York I Filed May 31, 1967, Ser. No. 642,464

Int. Cl. Hb 37/02, 39/02, 41/04 vs. Cl. 315-183 6 Claims ABSTRACT OF THE DISCLOSURE 3,476,977 Patented Nov. 4, 1969 a to 30' second interval. In commercial or factory type installations where the mercury vapor lamps provide the only illumination, the lamps must be able to be restarted immediately or else disrupt the normal workings of the factory. Therefore, apparatus for'oper ating mercury vapor lamps in such applications should start. a mercury lamp while in a hot condition in a relatively short interval so as to eliminate excessive outage periods. In addition, it is desirable that such apparatus be readily adapted forautomatic starting, and that certain components ofthe apparatus #be protected from the high voltage pulses used to effect hot starting. It is also advantageous that the bal ast apparatus employ circuit components that are relatively inexpensive. It is, therefore, an object of this invention to provide improved apparatus for operating electric discharge lamps which enables hot lamps to be started within a relatively circuit with its primary. A high leakage reactance. transformer is used to provide cold starting and operating voltage in the lamp operating circuit. In a specific aspect, the pulse generating source operates only when the lamp is out as the capacitor is connected to the operating circuit for charging in response to an open circuit condition in .the operating circuit.

BACKGROUND OF THE INVENTION .This invention'relates generally to apparatus forstarting and operating electric discharge lamps, and more particularly to apparatus adapted" for hot starting electric discharge lamps, such as mercury vapor lamps, within'a short time after they are extinguished.

Mercury vapor lamps include two main starting electrodes positioned in a glass envelope which is filled with an ionizable gas having certain amounts of mercury vapor together with traces of other elements if desired. To start or ignite a lamp of this type in cold condition, it is required that the ballast apparatus supply a peak 'voltage that is approximately 1.5 times higher than the peak operatingvoltage for the lamp. Ballast apparatus are available for cold starting high pressure lamps, utilizing either the open circuit voltage of the ballasting'transformer, or some auxiliary starting means to provide the cold starting voltage. I

One problem with prior art mercury vapor lamp ballast apparatus is that when a hot lamp (or one operating for at least one minute) is extinguished, as for example as a result of a power interruption, the ballast apparatus cannot restart the lamp immediately while in the hot condition. Mercury vapor lamps are characterized by relatively high internal temperature as compared with fiuoroescent lamps, and the gas' in the lamp envelope is short period of time after they are extinguished.

It is another object of this invention to provide an improved ballast apparatus for electric discharge lamps such as mercury vapor lamps wherein possible damage to certain operating components of the apparatus is minimized.

It is a still further object of the present invention to provide hot starting apparatus which is responsive to a lamp outage for starting the lamp while in a hot condition.

It is another object of the present invention to provide improved apparatus for operating mercury vapor lamps wherein hot lamps can be restarted within 20 to 30 seconds after they are extinguished.

SUMMARY OF THE INVENTION According to one form of my invention, I have provided an improved apparatus for operating electric discharge lamps of the type that require a hot starting peak voltage at least 1.5 times higher than the cold starting peak voltage. The exemplified apparatus employs a high leakage reactance transformer having primary and secondary windings, lead means for connecting the secondary winding and a mercury vapor lamp in an operating circuit in order to start the lamp in a cold condition and to operate the lamp. The apparatus includes a pulse generating source including a pulse transformer connected in the operating circuit for supplying pulses in orderto start the lamp when in a hot condition, as when the power supplied to the lamp interrupted. j v In one embodiment of my invention, a spark gap and a capacitor are connected in circuit with input means of the pulse transformer, and the output means of the pulse transformer is connected in the operating circuit. A switch is connected in circuit with the capacitor and a source of 7 current for charging the capacitor tothe breakdownvoltat a relatively high.pressure.'It'therefore takes'a higher peak voltage torestart a lamp when in a hot-condition thanwhen in=a cold condition. With a conventional ballast apparatus, it is necessary that the mercury vapor lamp cool down sufiiciently for the'gas' pressure to drop to a point where the cold starting voltage is effective to strike an arc across the lamp electrodes. In some instances, this cooling down period may be as long-as five minutes; Although forced air cooling has been utilized to reduce'the cooling down time, nonetheless the period during which the lamp is outis three minutes or more. 4

In. certain applications, such as in electrostatic copy machines and factory lighting situations, lamp outages for excessive periods of time are objectionable. Incopy machine applications, it is desirable to extinguish a hot mercury vapor lamp and to restart the hot lamp within age level of the spark gap.

In another embodiment of the invention I provide semiconductor switching means connected in circuit with the capacitor and the input means of 'the pulse transformer for effecting a discharge path fog the capacitor when a predetermined voltage level is reached on the capacitor. "In accordance with another aspect of my invention, I provide means for connecting the capacitor in circuit with the operating circuit for charging the capacitor to the breakdown voltage level of the spark gap when power to-the mercury vapor lamp has been interrupted. In one embodiment, the connecting means is a lead connecting the capacitor to the operating circuit for activating the pulse generating source in response to an open circuit condition of the lamp. In another embodiment, a voltage is set forth in the appended claims. The invention itself,

however, together with'further objects and advantages thereof may be understood by referring to the accompanying description taken in connection with the accompany FIGURE 1 is a schematic diagram of an improved apparatus for operating electric discharge lamps, the apparatus embodying one form of my invention;

FIGURE 2 is a partial schematic diagram illustrating a modification of the improved apparatus shown in FIG- URE 1, wherein semiconductor switching means is provided in accordance with another form of my invention;

FIGURE 3 is a partial schematic diagram illustrating another modification of the improved apparatus of FIG- URE 1, showing another form of my invention;

FIGURE 4 is a partial schematic diagram illustrating a modification of the apparatus shown in FIGURE 3, incorporating yet another form of my invention; and

FIGURE 5 is a schematic diagram illustrating a modification of my invention, in one form, as applied to alternating current apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now more particularly to the drawings, and especially to FIGURE 1 thereof, an apparatus is provided for starting and operating an electric discharge lamp 12 consisting of a tubular envelope 14 of light transmissive material and electrodes 16 and 18 positioned at opposite ends of the envelope 14. In the exemplification, the lamp 12 may be any high pressure electric discharge lamp such as a mercury vapor lamp having mercury vapor at approximately 2 to 3 atmospheres pressure together with traces of an element such as argon for ease of startmg.

In order to start the lamp 12 when in a cold condition, a pair of input leads 17 and 19 are adapted for connection to a suitable alternating current supply (not illustrated). The input leads 17 and 19 are also connected in circuit with a ballasting or current limiting device such as a high leakage reactance transformer 20 having a primary winding 22 and a secondary winding 24 inductively coupled on a magnetic core 26. In accordance with a wellknown means for limiting current flow in a lamp operating circuit, the high leakage reactance transformer 20 has magnetic shunts 28 for providing a predetermined amount of the transformer for use with lamps having different application of the exemplified apparatus 10 to obtain substantially flicker-free output from the lamp 12, the lamp is operated from direct current. The direct current is supplied from the output terminals 30 and 32 of a bridge rectifier 34, also having input terminals 36 and 38 connected in circuit with the secondary winding 24. The exemplified bridge rectifier 34 utilizes four half-wave rectifying diodes 35a, 35b, 35c and 35d connected in the conventional manner. I

As will be seen in FIGURE 1, the bridge rectifier input terminal 36 is connected to the secondary winding 24 by means of a terminal post 40 on a terminal board 42 which in turn is mounted on the enclosure or case 44 in which the apparatus 10 is housed. The terminal board 42 also includes two additional posts 46 and 48, connected to taps 50 and 52 respectively on the secondary winding 24. These taps are provided in order to compensate for aging of the lamp and also to adjust the output voltage of the transformer for use with lamps having different nominal voltages.

For connecting the lamp 12 and the transformer secondary winding 24 in an operating circuit, lead means or a pair of output leads 54 and 56 are connected in circuit with the bridge rectifier output terminals 30 and 32 respectively and with a pair of apparatus output terminals 58 and 60. Also included in the operating circuit is a direct current filter including a filter capacitor 62 connect d cro s u put leads 54 a d 5 nd a filter r ac r 4 or choke coil 64, the coil 64 being connected in series with the lead '54. The exemplified apparatus 10 also includes an extension winding 66, which may be concentrically wound with the primary winding 22 if so desired, and a power factor correction capacitor 65 connected across the extension winding 66 and input supply lead 19.

The mercury vapor lamp 12, as for example a commercially available H6T3 ultraviolet lamp, may be started when in a cold condition and operated by the above described circuit elements of apparatus 10. The cold starting peak voltage required for the exemplified H6T3 lamp is approximately 1,000 volts direct current, which appears across the filter capacitor 62 under the open circuit condition. The operating voltage for'this lamp is approximately 500 volts direct current, supplied in the operating circuit by 'secondary winding 24 and the bridge rectifier 34.

While the open circuit voltage at the apparatus output terminals 58 and 60 will start the lamp 12 when it is cold, when the lamp is hot, i.e., after it has operated for at least one minute and prior to its being cooled for at least 2 3 minutes, the open circuit voltage is ineffectual to start the lamp. I have determined that in order to start a mercury vapor lamp, such as the H6T3 lamp of the exemplification, within 20 to 30 seconds after it has been extinguished, hot starting pulses having a peak magnitude at least 1.5 times greater than the peak magnitude of the cold starting voltage are required. In order to start the lamp 12 while it is hot, I have provided a pulse generating source 67 including a switching means responsive to a predetermined voltage level in the form of a spark gap 68, an energy storage means in the form of a capacitor 70, a charging resistor 72 and a pulse tranformer 74.

The pulse transformer 74 has a winding 76 on one leg of a magnetic core 78, the winding 76 including taps 79, 80, and 81. The taps 79 and 80 are connected to input means or a primary section and the taps 79 and 81 are connected to output means or a secondary section, the secondary being connected in the operating circuit as the taps 79 and 81 are connected in series relation with the output lead 54. To enable the pulse generating source 67 to supply pulses in the operating circuit, the capacitor and spark gap 68 are connected in circuit with the transformer taps 79 and 80, i.e., with the primary, and also are connected through the charging resistor 72 to a normally open switch 82. The switch 82 in the exemplification is a pushbutton type switching means which is mounted on the enclosure 44, and is connected by lead 84 to the input lead 19. Another lead 86 connects the extension winding66 to the capacitor 70 and the transformer tap 80.

In order to start the lamp 12 immediately (i.e., within 20-30 seconds) after it has become extinguished and while still hot, the switching means 82 is closed and the pulse generating capacitor 70 will charge through the charging resistor 72 at a rate determined by the value of the resistor. When the charge on the capacitor 70 reaches the breakdown voltage level of the spark gap 68, the capacitor 70 will discharge through the gap 68 and the primary of the pulse transformer 74. A series of oscillatory pulses of a magnitude approximately equal to the breakdown voltage of the spark gap 68 will thereby be applied across the secondary of the pulse transformer 74. In this manner, stepped up hot starting pulses appear in the operating circuit, and hence are applied across the lamp 12. Upon discharging through the spark gap 68, the voltage level on the capacitor 70 immediately drops to render the spark gap 68 nonconducting, and the capacitor will then begin to recharge through the charging resistor 72. Of course, when the lamp 12 has restarted, the switching means 82 is released and will normally be in the open condition during the usual operation of the apparatus 10.

. I have found that it is desirable for the starting pulses applied across the hot lamp 12 to be of a high frequency, or short duration, in addition to having a peak magnitude at least 1.5 times greater than the peak magnitude of the starting voltage for the lamp when it is in a cold condition. Therefore, the source 67 in the exemplification was designed to supply 1-2 microsecond pulses of approximately 2,000 volts peak magnitude into the operating circuit. The reason for using short duration pulses is that many pulses of a lesser magnitude will supply an equivalent amount of energy as fewer, greater magnitude pulses, while requiring smaller, less expensive components, such as the pulse transformer 74 and the capacitor 70. In addition, by using high frequency pulses for starting the lamp in a hot condition, the total capacitive reactance across the lamp will be effectively lower, and hence the voltage required to strike an arc across the lamp electrodes 16 and 18 will be lower.

It is also desirable to isolate the starting pulses from the components of the operating circuit which may be damaged 'by the pulses, such as the diodes in the bridge rectifier 34 and from the AC. source. In the exemplified apparatus 10, this isolation is accomplished by means of the high reactance path provided by the filter or choke coil 64. Accordingly, lower rated, relatively inexpensive diodes were used in the exemplified bridge rectifier 34, as these diodes need only withstand a peak inverse voltage equal to the operating voltage applied in the operating circuit, and not equal to the peak magnitude of the starting pulses.

By way of a more specific exemplification of the invention, the apparatus shown in FIGURE 1 was reduced to practice, and the following components are given by way of illustration.

Lamp 12: 720 watt, H6T3 UV lamp Primary winding 22: 109 turns of 0.0679 of an inch in diameter wire Secondary winding 24: 378 turns of 0.0380 of an inch in diameter wire Extension winding 66: 481 turns of 0.0359 of an inch in diameter wire I Capacitor 67: 6.0 microfarads, 1,000 volts (D.C.)

Capacitor 70: 0.5 microfarad, 200 volts (D.C.)

Resistor 72: 3,000 ohms, 20 watts Spark gap 68: 185 volts, argon stabilized with 0.4 mm.

gap spacing Diodes 35a-35d: 4JA1011 Pulse transformer 74: W04 ferrite core autotransformer; ratio of primary to secondary turns 1:11; cross section of core 0.5 x 0.5 inch; window 1.26 x 0.95 inch In FIGURES 2, 3 and 4, I have illustrated exemplifications of various pulse generating sources which may be utilized with the apparatus shown in FIGURE 1. Since the high reactance transformer and bridge rectifier configuration for the apparatus of FIGURES 2-4 are essentially the same as shown in FIGURE 1, in FIGURES 2-4 I have only shown the pertinent portions of the apparatus including the pulse generating source. In these figures, like numbers are used to identify like parts.

For hot starting the lamp 12 with the arrangement shown in FIGURE 2, the switching means 82 is momentarily depressed thereby operatively connecting a bridge rectifier 90 across the extension winding of the high reactance transformer by leads 84 and 86. A filter capacitor 92 is connected across output terminals 94 and 96 of the bridge rectifier 90, and a charging resistor 97 is connected in series with an energy storage means or capacitor 98 in order to charge the capacitor 98 at a predetermined rate.

A semiconductor switching means including a. Zener diode 100 and a silicon controlled rectifier 102 is connected in circuit with the capacitor 98 and the input means or primary of the pulse transformer through taps 79, 80 for effecting a discharge of the capacitor when a predetermined voltage level thereon is reached. The silicon controlled rectifier 102 and capacitor 98 are connected in an operating loop with the primary of the pulse transformer '74 by leads 103 and 105. As the Zener diode 100 is connected to the gate 104 of the silicon controlled rectifier 102, when the voltage level on the capacitor 98 reaches the breakover voltage level of the Zener diode 100, the silicon controlled rectifier 102 will be switched on, thereby permitting the capacitor 98 to discharge through the pulse transformer primary. The pulse transformer 74 used in the exemplification of FIGURE 2 had a ratio of turns between the primary and secondary of approximately 1:25, and the transformer 74 supplied starting pulses of approximately 2,000 volts to the operating circuit and across the lamp for starting the lamp when in a hot condition. Various other circuit elements of the exemplification shown in FIGURE 2 are as follows: resistor 97150 ohms, 4 watts; capacitor 9850 microfarads; Zener diode -100 volts, IN1375A; and SCR 102C20D.

Referring now to FIGURE 3, it will be seen that the switching means 82 has been eliminated, as well as the leads 84 and 86 and the connection of capacitor 70 to the extension winding 66. In this embodiment of the invention, I have provided means for charging the capacitor 70 of the pulse generating source 67 to a predetermined voltage level in response to an interruption of power to the lamp 12, i.e., an open circuit condition across the apparatus output terminals 58 and 60. This means takes the form of a lead 108 connecting the capacitor 70 to the operating circuit at a point designated by numeral 109 between the pulse transformer 74 and the lamp 12 for response to an open circuit condition across the terminals 5 8 and 60.

When the lamp 12 is operating, the capacitor 70 will be charged to the level of the operating voltage in the operating circuit, this level being below the breakdown voltage level of the spark gap 68. However, when the lamp 12 is extinguished, as when power in the operating circuit has been momentarily interrupted, the capacitor 70 will become charged to the higher, open circuit voltage in the operating circuit, which is above the breakdown voltage of the spark gap 68. The spark gap 68 will then break down, permitting the capacitor 70 to discharge therethrough to the primary of the pulse transformer. The pulse transformer 74 will thereby supply high frequency, hot starting pulses to the operating circuit, causing the lamp 12 to start. When the lamp 12 has been restarted, immediately after power thereto was interrupted, it will represent a closed circuit across the output terminals 58 and 60, and the voltage applied to the capacitor 70 will again be below the breakdown voltage of the spark gap 68. In this manner, the pulse generating source 67 becomes operative in response to an open circuit or off condition of the lamp 12, and becomes inoperative when the lamp is restarted.

In FIGURE 4, I have illustrated a modification of the arrangement described in connection with FIGURE 3. In the arrangement of FIGURE 4, a semiconductor switching means generally denoted by numeral 111 is provided in conjunction with means for charging the capacitor 70 of the pulse generating source 67 in response to an open circuit condition across the output terminals 58 and 60. The: semiconductor switching means 111 provides a discharge path for the capacitor 70. Thus, the capacitor 70 is connected in circuit with the pulse transformer primary through taps 79, 80 and also with the operating circuit at a point between the pulse transformer 74 and the output terminals 58 and 60 through a voltage divider means. The voltage divider means comprises the two resistors 110 and'112, connected across the output leads 54 and 56 of the operating circuit. The charging resistor 72 in this embodiment is connected between the voltage dividing resistors and the capacitor 70 to charge the capacitor at a predetermined rate.

The semiconductor switching means 111 includes a Zener diode 114 and a silicon controlled rectifier 116, with the silicon controlled rectifier 116 being connected by leads 115, 117 in an operating loop with the capacitor 70 and pulse transformer primary thereby providing a discharge path for capacitor 70 to taps 79, 80 of the pulse transformer 74. The breakdown voltage of Zener diode 114 is greater than the resultant of the operating voltage of the operating circuit minus the voltage drop across either resistor 110 or 112, and less than the resultant of the open circuit voltage in the operating circuit minus the voltage drop across either resistor 110 or 112. The capacitor 70 will therefore be charged to the breakdown voltage level of the Zener diode 114 only when power to the lamp 12 is interrupted.

When the lamp 12 is turned off, the capacitor 70 will be charged by a voltage equal to the open circuit voltage of the operating circuit less the voltage drop across either resistor 110 or 112, to the breakdown voltage level of the Zener diode 114, and then discharge through the then switched on silicon controlled rectifier 116 into the primary of the pulse transformer 74. In this manner the pulse transformer 74 will supply stepped-up starting pulses to the operating circuit, causing the lamp 12 to restart while still in the hot condition. When the lamp 12 has been restarted, the voltage level on the capacitor 70 will then be insufficient to maintain the Zener diode 114 in a conductive condition, and the pulse generating source 67 will cease operating until such time as the lamp 12 is again extinguished.

Referring now to FIGURE 5, I have illustrated an apparatus 120 in which alternating current is supplied to an electric discharge device, such as a mercury vapor lamp 212, for operating the lamp. The apparatus 120 includes a pulse generating source 132 for starting the lamp 212 in a hot condition in accordance with my invention.

The apparatus 120 includes a high leakage reactance transformer 122 having a primary winding 124, shunts 125, and a secondary winding 126, with a power factor correction capacitor 128 connected to the secondary winding 126 by an output lead 129. During cold starting conditions, connection of the transformer primary winding 124 across a suitable power supply, such as a 115 volt, 60 cycle alternating current source by leads 167, 119 will provide sufficient open circuit voltage in the lamp operating circuit to start the lamp 212.

The lamp operating circuit includes the secondary winding 126, output leads 129 and 130, power factor correction capacitor 128, filter capacitor 131, and apparatus output terminals 127 and 169. Lamp 212 which is connected across terminals 127 and 169 will normally remain in operation so long as it is supplied with operating voltage in the operating circuit by the secondary winding 126. However, when the lamp is extinguished while hot, as when power thereto is momentarily interrupted, the open circuit voltage is insufficient to restart it immediately, as explained above. I have therefore provided the pulse generating source 132 generally similar to that described in connection with FIGURE 2 above, including a pulse transformer 134, a capacitor 139, a charging resistor 141, a pushbutton switch 138 and a semiconductor switching means 140. The pulse generating source 132 will supply pulses in the operating circuit in order to start the hot lamp 212 within 20 to 30 seconds after it has been extinguished.

The pulse generating source 132 includes a bridge rectifier 142 connected across the input leads 167 and 119 by leads 143 and 145. A filter capacitor 144 isconnected across the output terminals 146 and 148 of the bridge rectifier 142 for supplying rectified direct current to the leads 149 and 150 in order to charge the capacitor 139 when the pushbutton switch 138 is closed. As described in connection with FIGURE 2 above, when the capacitor '139 is charged to a predetermined voltage level, the semiconductor switching means 140 in the form of a Zener diode 156 which is connected to the gate 157 of a silicon controlled rectifier 158 will supply starting pulses to start the hot lamp. Thus, at the predetermined voltage level, the doide 156 will break down, rendering the silicon controlled rectifier 158 conductive. This will permit the capacitor 139 to discharge into the primary of the pulse transformer 134, supplying oscillating pulses thereto. When the capacitor 152 has discharged sufiiciently, the silicon controlled rectifier 158 will cease conducting, and the capacitor 139 will again be charged at a rate as determined by the value of the charging resistor 141. In this manner, a series of short duration (1-2 microsecond) starting pulses having a peak magnitude of approximately 2000 volts are supplied to the operating circuit to which the taps 152 and of the transformer 134 are connected, and the lamp 12 may thus be started while in a hot condition. Of course, once the lamp is started, the pushbutton switch will be released, rendering the pulse generating source 132 inoperative and the lamp 212 will be supplied with current from the operating circuit.

From the foregoing description of several illustrative embodiments of my invention, it will be appreciated that I have provided an improved arrangement for starting a mercury vapor or other high pressure electric discharge lamp while the lamp is in a hot condition. By virtue of the placement of the filter choke or coil 64 in the operating circuit between the pulse generating source and bridge rectifier, a high impedance path is provided between the pulse generating source 67 and the remainder of the apparatus. I am therefore able to employ relatively small and inexpensive components such as diode 35a-35d. Furthermore, by providing a series of high frequency pulses to a lamp in accordance with my invention, the magnitude of the pulses does not have to be inordinately high, thereby permitting the use of a relatively inexpensive pulse transformer. Although in the illustrated exemplifications of the invention, I have shown apparatus for operating a single mercury vapor lamp, it will be appreciated that two or more lamps may also be started and operated by use of the disclosed apparatus. In addition, the modifications of FIGURES 3 and 4 may be readily incorporated in the apparatus shown in FIGURE 5, if desired.

While I have illustrated and described several specific embodiments of the invention, further modifications and improvements will occur to those skilled in the art. It is understood, therefore, that this invention is not limited to the specific forms of the invention shown, and it is intended in the appended claims to cover all such modifications that come within the true spirit and scope of this invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An apparatus for operating an electric discharge lamp requiring a hot starting peak voltage at least 1.5 times higher than the cold starting peak voltage, the apparatus comprising: a high leakage reactance transformer having a primary winding for connection to a source of alternating current and a secondary winding inductively coupled with said primary winding; output lead means for connecting said secondary winding and at least one electric discharge lamp in an operating circuit wherein said secondary winding provides the voltage for starting said at least one electric discharge lamp in a cold condition and for operating said at least one electric discharge lamp; a pulse generating source for supplying pulses to said at least one electric discharge lamp for starting said at least one electric discharge lamp in a hot condition when power thereto has been interrupted, impedance means for providing a high impedance path between said pulse generating source and said secondary winding of said high reactance transformer thereby preventing said pulses from being fed back into said alternating current source, said pulse generating source including a pulse transformer having input means and output means with said output means being connected in the operating circuit, switch means responsive to a predetermined voltage level and energy storage means, said switching means and energy storage means being connected in circuit with the input means in said pulse transformer, and means for charging said energy storage means to the predetermined voltage level whereby said pulse generating source will supply said pulses in the operating circuit to start the at least one electric discharge lamp in a hot condition.

2. The apparatus of claim 1 wherein said pulse transformer comprising a ferrite core transformer having a winding on one leg of the core, said input means comprising a primary section of said winding and said output means comprising a secondary section of said winding.

3. An apparatus for operating an electric discharge lamp requiring a hot starting peak voltage at least 1.5 times higher than the cold starting peak voltage, the apparatus comprising: means for starting said lamp in a cold condition and for limiting the current supplied to the lamp; input circuit means for connecting said means to a source of alternating current; output circuit means for connecting said means and at least one electric discharge lamp in an operating circuit; a pulse generating source for supplying pulses to said at least one electric discharge lamp for starting the at least one electric discharge lamp in a hot condition, impedance means for providing a high impedance path between said pulse generating source and said secondary winding of said high reactance transformer thereby preventing said pulses from being fed back into said alternating current source, said pulse generating source including a pulse transformer having a primary and a secondary with the secondary being connected in the operating circuit, switching means connected in circuit with said primary, said switching means being responsive to a predetermined voltage level, energy storage means connected in circuit with said operating circuit for charging said energy storage means to said predetermined voltage level when power to said at least one electric discharge lamp is interrupted whereby said pulse generating source will supply said pulses for starting the electric discharge lamp in a hot condition.

4. The apparatus of claim 3 wherein said switching means includes a controlled rectifier connected in an operating loop with said energy storage means and said primary, and a voltage breakdown device connected in circuit with said controlled rectifier and said energy storage means for rendering said controlled rectifier conductive when the predetermined voltage level is reached on said energy storage means for effecting a discharge of said energy storage means into said primary.

5. An apparatus for operating an electric discharge lamp requiring a hot starting peak voltage at least 1.5 times higher than the cold starting peak voltage, the apparatus comprising: a high reactance transformer having a primary winding for connection to a source of alternating current and a secondary winding inductively coupled with said primary winding; rectifying means connected in circuit with said secondary winding; circuit means for connecting said secondary winding, said rectifying means and at least one electric discharge lamp in an operating circuit wherein the high reactance transformer will provide a unidirectional voltage for starting said at least one electric discharge lamp in a cold condition and for operating said at least one electric discharge lamp; a pulse generating source for supplying pulses to said at least one electric discharge lamp for starting the electric discharge lamp when in a hot condition, said pulse generating source including a pulse transformer having input means and output means with said output means being connected in the operating circuit, switching means responsive to a predetermined voltage level and energy storage means, said switching means and energy storage means being connected in circuit with the input means of said pulse transformer, means for charging said energy storage means to said predetermined voltage level whereby said pulse generating source will supply said pulses in the operating circuit, and means providing a high impedance path between said pulse generating source and said rectifying means for preventing a feedback of said pulses into said source and said rectifying means.

6. The apparatus of claim 5 wherein said charging means comprises circuit means connecting said energy storage means in circuit with said operating circuit for charging said energy storage means to said predetermined voltage level when power to said at least one discharge lamp is interrupted.

References Cited UNITED STATES PATENTS 2,717,335 9/1955 Sims et al. 315-289 X 3,037,147 5/1962 Genuit et al. 315-298 X 3,235,769 2/1966 Wattenbach 315l76 3,235,770 2/1966 Wattenbach 315239 3,259,796 7/1966 Hallay 315l74 JAMES W. LAWRENCE, Primary Examiner C. R. CAMPBELL, Assistant Examiner U.S. Cl. X.R. 315-205, 274, 289 

